This invention relates to servicing of elevators, and more particularly relates to apparatus and methods for servicing an elevator roller guide wheel assembly by replacing the tires thereof.
It is well known in the prior art that an elevator car travels vertically in hoistways using a pair of parallel T-shaped guide rails. It is also well known in the prior art that the travel of an elevator car is effectuated by the cooperation between the T-shaped guide rails and roller guides which are affixed on each of the four sides thereof, proximal to its top and bottom portions.
More particularly, in U.S. Pat. No. 3,087,583, Bruns describes the operation of rolling wheel type guides which are resiliently mounted on an elevator car and which cooperate with three guiding surfaces of each rail, thereby controlling the travel of the elevator car. The wheels are mounted on axles which enable the rim thereof to move on the guide rail surface, while being biased into contact with this surface by a plurality of springs. These roller guides include a pedestal to maintain contact between the guide assembly and the elevator car.
Bruns further describes the limitations of the prior art whereby misalignment of guide rails may cause a car's travel to deviate from its intended path. This, in turn, may cause swaying of the car while traversing the hoistway and produce concomitant forces upon the roller guide wheels. Accordingly, Bruns teaches an extended roller guide which inherently mitigates the impact of guide rail discontinuities by cushioning roller travel.
Similarly, Tucker, in U.S. Pat. No. 3,099,334 discloses an improved elevator roller guide for minimizing perturbations to the preferred position of elevator cars on their respective guide rail surfaces. By avoiding this hereinbefore described tendency of an elevator car to sway as it traverses the hoistway, particularly at high speeds, the associated noises are reduce. Unfortunately, the conventional method of increasing the pressure of a roller guide against the surface of the guide rails also increases noise. Accordingly, the Tucker improved roller guide provides only minimal pressure against the respective guide rail surfaces and also provides dampening means to reduce the tendency of a car to sway.
Another limitation known in the prior art is the interdependence between imbalance and misalignment in the rollers comprising a roller guide assembly. In particular, as described in U.S. Pat. No. 3,329,240, in spite of careful alignment of roller guides with T-shape guide rails, misalignment of side rollers is effectuated as a consequence of there being an imbalance causing deflection of face rollers. Conversely, an imbalance causing a deflection of side rollers, effectuates a misalignment of face rollers. In U.S. Pat. No. 3,329,240, Harwood discloses an improved roller guide assembly which avoids the hereinbefore described misalignment of face and side rollers with respect to corresponding guide rail surfaces, notwithstanding there being an imbalance in an elevator car, or there being misalignment or deflection in the guide rails. More particularly, the Harwood roller guide comprises a rigid roller mounting cage having a face roller receiving portion and a side roller mounting portion. Six rollers are rotatably mounted on the cage, with the cage having flexible loading means which is adapted to preload the face rollers against the face roller contact portion of the guide rail.
Elevator wheels typically consist of a metal housing which contains its rolling surface and retained wheel bearings. The rolling surface or "tire" is conventionally made from malleable materials like rubber or polyurethane. It is well known to those skilled in the art that the common reason for roller guide failure is bond separation between the metal hub of a wheel and the tire. Such bond separation causes the tire to break away from the roller guide assembly, thereby interfering with the normal travel of an elevator car as it proceeds vertically up and down the hoistway.
It is apparent to those skilled in the art that the usual remedy for a broken roller guide wheel is to remove and replace the entire wheel assembly. Such an assembly conventionally consists of a metal hub with a tire bonded thereto, and ball bearings contained in a concentric retainer ring. Depending upon the manufacturer, sometimes the repair also includes a replacement shaft. For example, servicing a damaged roller guide for an Otis Elevator typically includes replacement of the shaft.
It is a disadvantage of the prior art that notwithstanding that such roller guide failures are usually not caused by bearing failures, during the servicing of a roller guide wheel, the existing bearings are conventionally discarded. It is also a disadvantage of the prior art that repairing a roller guide wheel with a separated tire necessitates replacing the entire wheel assembly instead of merely replacing the tire thereof.
Accordingly, these limitations and disadvantages of the prior art have been overcome with the present invention, and improved apparatus and techniques are provided which are especially useful for servicing an elevator roller guide wheel assembly, and for the replacement of the tire thereof.